Although resin molded bodies are used as a replacement for metals from the viewpoint of reducing the weights of various types of components, it may often be difficult to replace all metal components with resins. In such a case, it can be considered that a new composite component is manufactured by integrally joining a metal molded body and a resin molded body.
However, a technology capable of integrally joining a metal molded body and a resin molded body in an industrially advantageous manner and with a high joining strength is not commercially available.
JP-B 4020957 discloses a method of performing laser processing on a metal surface for joining different types of materials (resins) including a process of performing laser scanning on the metal surface in one scanning direction and a process of performing laser scanning in a scanning direction that crosses it.
JP-A 2010-167475 discloses a laser processing method of performing laser scanning a plurality of times further in a superimposed manner, in the invention of JP-B 4020957.
However, since in the inventions disclosed in JP-B 4020957 and JP-A 2010-167475, it is necessary to perform laser scanning in two directions crossing each other without fail, there is room for improvement in that it takes a long time to perform the processing.
Furthermore, although it is considered that sufficient surface roughening processing can be performed by the laser scanning in the crossing directions to thereby be capable of increasing the joining strength, the surface roughness state is not uniform, with the result that there exists a problem in which the directivity of the strength of the joining part of a metal and a resin may be instable.
For example, there may be generated a problem in which one jointed body has the highest shear force and tensile strength in an X axis direction, but another jointed body has the highest shear force and tensile strength in a Y axis direction different from the X axis direction, and furthermore, yet another jointed body has the highest shear force and tensile strength in a Z axis direction different from the X axis direction and the Y axis direction.
Although there are cases where a composite body of a metal and a resin having a high joining strength in a specific direction is required depending on products (for example, a rotating body component in one direction and a reciprocating component in one direction), the above-described request cannot be sufficiently met in the inventions disclosed in JP-B 4020957 and JP-A 2010-167475.
Furthermore, in the case where a joint surface has a complicated shape or a shape including a thin width part (for example, a star shape, a triangle shape or a dumbbell shape), it can also be considered that a sufficient joining strength cannot be obtained as a result of the fact that surface roughening processing is partially non-uniform by the method of performing laser scanning in the crossing directions.
JP-A 10-294024 discloses a method of manufacturing an electrical and electronic component in which a concavity and a convexity is formed by irradiating a metal surface with laser light and in which injection molding is performed on the concavity and convexity-forming site with a resin, a rubber or the like.
Embodiments 1 to 3 describe that the concavity and convexity is formed by irradiating the surface of a long metal coil with a laser. Then, paragraph [0010] describes that the surface of the long metal coil is roughened so as to be striped or satin-shaped, and paragraph [0019] discloses that the surface of the long metal coil is roughened so as to be striped, dotted, wavy, knurled or satin-shaped.
However, as described in the effects of the invention of paragraphs [0021] and [0022], the purpose of the laser irradiation is to form fine and irregular concavities and convexities in the surface of the metal to thereby enhance an anchor effect. In particular, since the long metal coil is a target to be processed, it is considered that fine and irregular concavities and convexities are inevitably formed even when any concavity and convexity are formed.
Therefore, the invention disclosed in JP-A 10-294024 discloses the same technical thought as in the invention in which laser irradiation is performed in the crossing directions to form fine concavities and convexities in the surface as in the inventions disclosed in JP-B 4020957 and JP-A 2010-167475.
WO-A1 2012/090671 discloses a method of manufacturing a composite molded body formed of a metal molded body and a resin molded body. The method includes a process of performing laser scanning so as to form straight and/or curved markings, on the joint surface of the metal molded body, in one direction or a different direction, and a process of performing laser scanning such that the straight and/or curved markings do not intersect with each other. In FIGS. 6 to 9, quadrangular, circular, oval and triangular marking patterns are shown.